Members of the Syrian Democratic Forces (SDF) cross a bridge after they entered the western front of Daesh's Syrian bastion of Raqqah after seizing the area on June 11, 2017. (Photo by AFP)

The so-called Syrian Democratic Forces (SDF), a US-backed group of mostly Kurdish forces, has recaptured the last road into Syria’s northern city of Raqqah, the de facto capital of the Daesh terrorist group in the Arab country.

Colonel Joe Scrocca, a spokesman for the US-led coalition allegedly fighting Daesh, said the SDF held all routes into Raqqah from the south.

"South of the Euphrates River, the SDF now controls all high-speed routes into Raqqa," the Associated Press quoted Scrocca as saying.

He also stressed that moving toward the Euphrates River from the east "would completely encircle the city and has been the SDF plan from the start."

The official further estimated that 2,500 Daesh elements still remained in Raqqah.

The fight for Raqqah has only began, he said, adding, "There is still much fighting to be done in the city."

Meanwhile, the so-called Syrian Observatory for Human Rights (SOHR) confirmed that a unit of the SDF had seized villages across the Euphrates and was moving through the Kasret al-Faraj area.

SOHR director Rami Abdurrahman described the fresh gain as a "strategic" advance that completes the siege around Raqqah, adding Daesh has no other choice now but to surrender or fight to the end.

Members of the so-called Syrian Democratic Forces (SDF) walk on the rubble of a damaged street in the Raqqah's al-Sana'a industrial neighborhood on June 14, 2017. (Photo by Reuters)

Last week, US-led coalition spokesman Ryan Dillon said Daesh terrorists had been "abandoned" by their leaders who themselves attempted to escape the Syrian city.

Daesh captured Raqqah in July 2014 and declared the city its stronghold in Syria.

Tightening the noose around Raqqah effectively denies the Daesh militants an escape route to the city of Dayr al-Zawr.

Over the past few months, Syrian forces have made sweeping gains against Takfiri elements who have lately increased their acts of violence across the country following a series of defeats on the ground.